To me, a true phablet eliminates the need and even the desire to carry or own two devices smaller than a laptop, even for people who are able to easily afford two devices.

Instead of thinking about phablet computing as a device category, think of it as a new behavior, paradigm, or lifestyle in which a small-tablet size device forms the centerpiece of mobility in an elegant, socially acceptable, and convenient way.

This just isn't happening yet. But why?

It turns out that the secret is not just figuring out the perfect intermediate screen size. The way to achieve the phablet lifestyle is to combine the right phablet with wirelessly connected wearable computing.

One company appears to have figured this out. In the past week, Sony announced three products, all shipping in September, that will usher in a true phablet scenario for those who embrace it.

The first of these products is—you guessed it!—a really, really big phone.

Sony's fantastic 'phablet' formula

Sony announced this week a giant phone called the Xperia Z Ultra. It's got a 6.4-inch screen.

That's slightly bigger even than Samsung's ginormous Galaxy Mega, which has a 6.3-inch screen.

It's also thin: At 6.5 millimeters, the Xperia Z Ultra is significantly thinner than an iPhone 5. That's ever so slightly over one quarter of an inch thick.

Functionally, the phone is like other smartphones, but with Sony's software on top. It's a very powerful phone, powered by a Qualcomm Snapdragon 800 2.2GHz quad-core processor and running Android 4.2 Jelly Bean.

In addition to being big and fast, the Xperia Z Ultra performs two really neat tricks. The first is that it's waterproof. No, I don't mean it's splash resistant. You can literally jump in a swimming pool with it and take pictures and videos underwater. (It's not for deep-sea diving. Sony recommends a maximum of five feet deep for a maximum of 30 minutes.)

The second neat trick is that you can use just about anything as a stylus, including a regular No. 2 pencil.

Such a giant phone is great when you're watching a movie, reading an e-book, playing a game or doing other things normally associated with tablets.

The trouble is: What happens when the phone rings? Do you pull this huge device out of your backpack or purse and hold it up to the side of your head?

Sony's wearable 'phablet' accessory

What happens when you want to check who's calling, check a social media notification alert, send a short text message, look up a quick Google Now query or do any number of the actions we all obsessively do all day with our phones.

Taking out a 6.4-inch screen device is a bigger deal than pulling out a phone. And that's one of the problems with "phablets."

When the phone rings, you answer it like it's a phone by holding it up to your ear. Or, you plug your earbuds into it like you would a regular phone. The difference is that it's a tiny fraction of the size of even the smallest smartphone.

It's also different because you pair it with the Xperia Z Ultra by simply tapping it against the phone. They both support NFC.

The Smart Bluetooth Handset SBH52 is basically a controller that clips onto your shirt or anything else and enables you to monitor and control audio beamed wirelessly from a phone or "phablet."

It's got a low-resolution screen to display the time, text messages, caller ID information or the current track. It plays music from your phone, and also has a built-in FM radio, which is great for gyms that broadcast the TV audio over treadmills via FM. A rocker switch adjusts the volume.

The SBH52 is optimized for managing phone calls. You can see who's calling and press a button to answer. You can also scroll around to see recent calls and call people back.

All this is taking place with a device the size of a pack of gum while your giant phablet is tucked away in a backpack or purse or is charging on the other side of the room.

If you're a business person, the light and tiny SBH52 is black and professional looking and clips discreetly into an inside coat pocket while the phablet is tucked away in a briefcase or purse. But when it comes time to pitch, the Xperia Z Ultra's screen is big enough to present slides to a client.

Sony's SmartWatch2 enables you to do many of the quick-and-dirty communication and entertainment tasks of a phone, without taking your giant "phablet" out.

Sony has not announced the price of the SBH52 or a specific ship date, but it's expected to come out by September. (Some rumor and speculation suggests that Sony may bundle the SBH52 in free with the Xperia Z Ultra.)

Sony's other wearable 'phablet' accessory

Sony also announced this week the forthcoming release of an upgrade for its smartwatch.

Called the Sony SmartWatch 2, Sony bills its newest wearable computing gadget as "a second screen for your Android smartphone."

While it works with any Android phone, it's especially useful for phablets. Itself an Android device, the SmartWatch 2 not only runs apps but pairs with a phone or phablet. When someone calls the giant phablet in your backpack, the watch alerts you and tells you who's calling. You can also play and control music, play games and check incoming texts and social messages.

Like the Bluetooth accessory, the SmartWatch 2 looks business-professional and supports NFC and pairs with a tap. It's also water- and dust-proof, according to Sony.

I highlight the Sony solutions not because I think everyone should go out and buy them. This is not a review, and I cannot vouch for these devices' quality or desirability. My focus is about Sony's vision for phablet computing, which I think is the right vision.

Other companies can do this, too. Or users can combine phablets with wearable computing for an improved mobile experience by mixing and matching components from different companies.

The advantage: Increased portability. You're ready to do anything a phone or a tablet can do, and you can do it quickly, conveniently and from anywhere—a restaurant, while walking down the street or, in the case of Sony's solution, while splashing around in the water.

Wearable computing does not need phablet computing—a smartphone is a perfectly good base for wearable.

But here's the revelation that hardly anyone except Sony seems to understand: Phablets need wearable devices to make them powerful, viable and mainstream, as well as acceptable in business.

I think phablets plus wearable is going to take mobility to a whole new level.